Policy changes, such as a tax on greenhouse gas releases — something already paid by 1.6 billion people in the world, are needed to combat the rise in global temperature, an economist said during a Monday conference in New Orleans.

Feel-good measures such as taking part in Earth Hour, where millions turned off their lights for an hour, don’t make a dent in where we’re headed with global temperature increases, Gernot Wagner, senior economist with the Environmental Defense Fund, told the crowd at the Challenges of Natural Resources Economics and Policy conference.

“It can’t possibly make a difference.”

Greenhouse gases in the atmosphere are up to 400 parts per million, the highest since the industrial revolution, and that number is expected to increase without action to stop it, he said.

“We’re not just walking in the wrong direction, we’re walking in the wrong direction more quickly,” said Wagner, who is also a research associate at the Harvard Kennedy School and an adjunct associate professor at the Columbia School of International and Public Affairs.

Meaningful measures call for creating incentives to bring down the amount of greenhouse gases, he said. Even China is looking at a cap-and-trade system and India has a $1 per ton tax on coal.

So far, that’s not the case in the United States, where it’s estimated that each American releases about 20 tons of greenhouse gases each year, about twice as much per person in Europe.

“That’s pretty well-known facts,” he said.

Greenhouse gas will eventually cause global temperatures to rise between 2.7 degrees to 8 degrees by 2100.

“This is a huge range,” Wagner said, and it’s that uncertainty that is going to be so costly.

If countries and policy makers had a better certainty of what would happen as greenhouse gases rise, efforts could be more concentrated, but that doesn’t look to be the case anytime soon.

But global temperature increases already have created problems that need to be addressed.

“Voluntary action simply can’t be the answer. It has to be policy,” he said.

Climate change was the topic of many of the conference sessions as researchers try to get a better handle on the social and economic impacts of sea level rise and climate change.

The conference is held every three years through the LSU Center for Natural Resource Economic Policy.

Follow Amy Wold on Twitter, @awold10.